HiFI OP-AMPs, BJTs, and FETs how do I choose them?

[777funk]

I'm fairly inexperienced in Semiconductor Electronics. I am a young degreed E.E. but that doesn't mean much in terms of experience in Audio electronics. The little experience I do have mis mostly in Tubes.

I'm looking to upgrade the audio equipment I have as well as recording gear.

How do I choose parts? I've read there are some popular opamps by burr brown (now TI) etc. But How in the world do I know what is good?


ALSO, when I'm replacing a transistor (I am now on a blown driver section on an old pioneer amplifier) how do I know what to get? I have two power transistors (D525 and B595) that are shorted. I need new ones. I'd like to get better ones if I can since this is an OLD piece of gear. But I have no idea where to start. I can't even find the originals at any place I've looked (part D525 and B595) which would be at mouser and digikey. Are there brands that I should look for/avoid?

thanks!!
Nick

[AndrewT]

Hi,
can you find the datasheet for the 2sb595 and 2sd525?

Download it and compare specs to currently available drivers.

[777funk]

Originally posted by AndrewT
Hi,
can you find the datasheet for the 2sb595 and 2sd525?

Download it and compare specs to currently available drivers.

Ok got the data sheet from NTE
http://www.nteinc.com/specs/10to99/pdf/nte54.pdf



Forgive me for ignorance here but how do I use those specs. Obviously I will want an NPN and PNP and to the Voltage and Current ratings. But here are my questions on that:
-If I go over the voltage and current ratings will that be ok? I'm assuming so
-What else should I look for?
-Can I tell from the Datasheet that the transistor will sound better or worse than the originals?

[AndrewT]

the url is not valid and cannot be loaded.

[777funk]

Sorry,
Hopefully this works:
http://www.nteinc.com/specs/10to99/pdf/nte54.pdf

[B Cullingford]

Maybe 2SD525 and 2SB595 are obsolete and hence will be difficult to find.

I would not trust NTE replacement specs to be valid, try to find an original data sheet, or data book

you know you could just search - you might find for example:
http://www.jmnic.com/pdf/2sd/2SD525.pdf

Besides the obvious V, I and power ratings you may need to consider beta, and ft; newer, possibly faster transistors could require modifying the circuit to prevent oscillation.

I could help more but my data books and stash of old transistors are thousands of miles away!!

[pacificblue]

http://www.datasheetcatalog.com/

[777funk]

Originally posted by B Cullingford
Maybe 2SD525 and 2SB595 are obsolete and hence will be difficult to find.

I would not trust NTE replacement specs to be valid, try to find an original data sheet, or data book

you know you could just search - you might find for example:
http://www.jmnic.com/pdf/2sd/2SD525.pdf

Besides the obvious V, I and power ratings you may need to consider beta, and ft; newer, possibly faster transistors could require modifying the circuit to prevent oscillation.

I could help more but my data books and stash of old transistors are thousands of miles away!!

OK faster... there's a hifi term I was looking for. How do I find the speed of a transistor. Bandwidth seems to be another hifi term I hear on semiconductors. Can I tell from data sheets which parts will sound better?

I'm not so much worried about replacing them with the originals. I'd like to upgrade if possible.

Originally posted by pacificblue
http://www.datasheetcatalog.com/

Thanks!!

[777funk]

Ok, I have some answers on how to find the parts for this amp... but still my original question:

HiFI OP-AMPs, BJTs, and FETs how do I choose them?


Is it something where I look at data sheets and find the numbers and specs.

How do I know how fast the component is?

Also, I hear the word Bandwidth thrown around all the time. What does that mean in the world of audio and transistors/opamps?

thanks,

[ostripper]

How do I know how fast the component is?
Also, I hear the word Bandwidth thrown around all the time. What does that mean in the world of audio and transistors/opamps

As far as a replacement for your devices , TIP41/42c
http://www.fairchildsemi.com/ds/TI/TIP41.pdf
are the best bet.
How did I choose these ?
1. Ft (bandwidth) is lower. BUT , this is an audio amp (not RF).
2sd/b's are 12mhz -=TIP' s are 3mhz. If the sub was 20-30 Mhz,
I might be worried that my amp would oscillate. (it was compensated for 12mhz devices.)

2. Pc (collector dissipation) the tip's are 65W and the 2sd/b's
are 40W. a Little more is better for a good repair.
SOA of the tip's is also better .

3. Hfe (dc current gain) 2sd/b's is 40 @ 300mA and the TIP's
are 44 @ 300ma , Close. One might have to re-adjust bias
just a little.. look at first typical characteristics plot in the tip41 datasheet.
4. Vceo - voltage rating tip41c = 2sd525 = 100v... right on.

And most important , experiance. 5. my first childhood amp
had these devices (2sd525/2sb595 / kenwood 20w int. amp)
and the tip's worked out like a charm.
OS